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Brainstem evoked response audiometry.

Brainstem evoked response audiometry is useful in the identification of threshold levels as well as in the diagnosis of eighth nerve tumors. The instrumentation is a modification of the electroencephalograph and an averaging computer; 3,000 clicks, 16/s, are presented and averaged for each printed response. Evoked responses can be obtained from a patient who is unable or unwilling to respond to conventional behavioral testing; best results are obtained from quiet or asleep patients.

Audiometry↗

Acoustic neuroma: results of brain stem evoked response audiometry.

Brain stem evoked response (BER) audiometry presents abnormal findings in patients with acoustic neuromas. The test involves averaging of recordings at the vertex as sound-triggered nerve impulses travel from the cochlea to the brain stem. From the time the sound stimulus arrives at the cochlea until it reaches the first major brain stem synapse (within 10 milliseconds), five major waves have been identified as typical of normal averaged responses. Abnormality in the cochlea or eighth nerve causes specific changes in pattern, primarily in wave latency. These latency shifts can be used to predict the site of the lesion. In evaluating 17 lesions of the cerebellopontine angle, BER audiometry was accurate in the diagnosis of all of the tumors. This diagnostic tool should play a prominent role when acoustic tumor is suspected.

Adolescent↗

Dilemmas in auditory assessment of developmentally retarded children using behavioural observation audiometry and brain stem evoked response audiometry.

The records of 94 consecutive developmentally retarded children with speech retardation and suspected hearing loss who underwent auditory assessment by both conventional behavioural observation audiometry (BOA) and brain stem evoked response audiometry (BERA) were analysed. In 54 children (57.4 per cent) there was good agreement between the results of both techniques leading to a clearcut diagnosis. In 22 children a diagnosis was possible only by the results of BERA as the results of BOA were inconclusive. Of the remaining 18 children, two groups could be identified whose results posed a dilemma. Group 1 (n = 7) consisted of children whose BOA test results differed considerably from their BERA results. Group 2 (n = 11) consisted of children in whom there was no discernible response by BERA while the response by BOA was either inconsistent (n = 5) or not elicitable (n = 6). The specific strategies to be adopted for hearing assessment in these situations are discussed.

Audiometry, Evoked Response↗

Brain stem evoked response audiometry in neonates.

Brain stem evoked response audiometry (BERA) was performed in 50 normal full term newborn infants (25 male, 25 female) to generate normative data base for this age group. The stimuli of 30 dB, 40 dB and 80 dB nHL (normal hearing level) intensities were delivered to each subjects. 30 dB stimulus failed to produce clear wave patterns, whereas upto six vertex positive waves were recognised among which waves I, III and V were commonly present. The absolute latencies of waves I and V at 40 dB nJL were 2.54 +/- 0.21 msec and 7.56 +/- 0.26 msec and at 80 dB nHL these were 2.06 +/- 0.15 msec and 7.09 +/- 0.17 msec respectively. I-V interpeak latencies (IPL) were 5.02 +/- 0.13 msec at 40 dB and 5.03 +/- 0.13 at 80 dB nHL. The latencies of waves I and V were decreased with the increase of intensity of stimuli with the rate of 0.012 msec/dB, bit I-V IPL, i.e., central conduction time remained almost constant. There were no statistically significant differences in the brain stem auditory evoked responses between male and female subjects. Brain stem evoked response audiometry is objective and reliable for hearing screening in neonates.

Audiometry, Evoked Response↗

Hearing assessment in developmentally impaired infants: classical conditioning as a supplement to brainstem-evoked response audiometry (BERA).

The brainstem-evoked response audiometry (BERA) is probably the most common approach to hearing assessment in high-risk and developmentally handicapped infants. It is usually suggested, however, that BERA should not be the sole assessment method. In an attempt to determine an effective supplement to BERA, the present study evaluated a classical conditioning procedure with developmentally impaired babies. Within this procedure, different tones served as conditioned stimuli while an air-puff was used as the unconditioned stimulus. Results indicate that this procedure could be successfully applied with almost all of the babies.

Audiometry, Evoked Response↗

Cortical evoked response audiometry thresholds and neuroleptic, sedative, hypnotic drugs.

Cortical evoked response audiometry is adequate for approximating hearing threshold levels with frequency specificity when the psychoacoustic responses lack reliability and reproducibility (compensation claim). It is well-known that control of wakefulness is essential for the reliability of slow vertex responses (SVR). Therefore, sedative, hypnotic, and neuroleptic drugs are supposed to have possible adverse effects on the detection of SVR. In contrast, brainstem evoked responses (BER) have proved not to be significantly affected by therapeutic doses of these compounds. The purpose of our study was to assess the reliability of SVR-threshold definition in subjects taking neuroleptic, sedative, and hypnotic drugs. Fifteen subjects examined for occupational hearing loss at the Fund for Occupational Diseases in Brussels and regularly taking one or several of these drugs were compared with 27 comparable controls. In each subject the auditory thresholds were defined with both techniques: SVR (1, 2, and 3 kHz) and BER (clicks). A highly significant difference is observed between the two groups: In the group receiving drugs, the SVR threshold for 3 kHz is 12.1 dB (average) higher than the BER threshold, whereas in the group without drugs, the SVR threshold for 3 kHz is 7.77 dB (average) lower than the BER threshold. In the drug group, large interindividual differences are observed. It may be concluded that the use of neuroleptics, sedatives, and hypnotics renders the auditory threshold definition with SVR completely unreliable. In using SVR for medicolegal threshold definition, controlling the 3-kHz threshold with BER always is necessary.

Adult↗

Feasibility studies of evoked response audiometry in the mentally subnormal.

Evoked response audiometry was attempted on a group of seventy-seven unsedated severly subnormal patients up to the age of twenty-two years. Data of some clinical value were obtained in fifty-seven cases. It is suggested that sedation need only be used if the initial attempt at E.R.A. is unsuccessful. Over twenty per cent of the subjects appeared to have significant hearing loss.

Acoustic Stimulation↗

Problems in interpretation of brainstem-evoked response audiometry results.

This report describes 6 cases - 3 adults and 3 children - in which no response could be obtained during the brainstem-evoked response audiometry (ABR) examination. This, in spite of the fact that maximal click intensity was used during the test, and despite the patients' nearly normal hearing sensitivity. All of the cases presented a slight degree of neurological deficiency, which could explain the faulty synchronization of the biological response to clicks. Attention is drawn to the fact that lack of response in ABR in cases with central nervous system involvement is not necessarily proof of severe hearing loss, and could supply important diagnostic cues.

Adult↗

Brainstem evoked response audiometry in confirmed eighth nerve tumors.

Brainstem evoked response audiometry has been described as an effective predictor of eighth nerve disease. This study reports audiologic findings in 52 cases of surgically confirmed eighth nerve and cerebellopontine angle tumors. The results of brainstem audiometry were consistent with an eighth nerve lesion in 51 cases. Its use in site of lesion tests is highly recommended.

Audiometry, Evoked Response↗

[Electrophysiologic studies of hearing: current methods in clinical and occupational audiology. I. Brain stem evoked response audiometry (ABR)].

Electrophysiological methods of auditory assessment called evoked responses are an exciting new development with broad implications in the fields of otology, audiology and neurology. At the present time they are the best objective non-invasive audiometric tests (versus subjective psychoacoustic examinations) for predicting hearing thresholds in infants and uncooperative patients. Basic concepts of electric response audiometry, most important auditory evoked potentials, their probable sites of generation and classification according to latency i.e. elapsed time between stimulus and response are reviewed. Instrumentation, procedure and technical considerations in recording the brain-stem evoked response audiometry (ABR), the most popular recent method for evoked potentials testing are described. Special attention is focused on measurement, identification and interpretation of brainstem responses and their major clinical uses, namely threshold testing of infants, young children and malingerers, diagnosis of acoustic tumors and neurological evaluation of brainstem lesions. Finally, the first own experience with a new employed in our laboratory the evoked potentials system Amplaid MK 10 for clinical testing of auditory pathways are presented and illustrated by some examples of application of brainstem audiometry in diagnosis of occupational noise-induced hearing loss.

Adult↗

Clinical interpretation of brainstem evoked response audiometry abnormalities in cochlear pathology.

This investigation involved 45 patients with sensorineural hearing loss (SNHL): 24 with Meniere's disease, 18 with acoustic trauma, and 3 with SNHL due to ototoxic drugs. They all underwent pure tone audiometry and standard brainstem evoked response audiometry (BERA). In patients without wave I in auditory brainstem response, electrocochelography (ECochG) was performed. The findings are presented showing that cochlear lesions (beside threshold elevation) cause latency prolongation of wave I, III and V relative to normal latencies at the actual click hearing level. At high stimulation levels, this effect is almost completely compensated for by the fact that cochlear recruiting ears exhibit steeper latency-intensity curves than do normal ears. But, at the same time this pathology does not cause latency prolongation of central conduction time (CCT). Beside this, cochlear lesions will cause, in some cases, deterioration of replicability (poor waveform resolution) of waves preceding wave V. In such cases, the authors strongly recommend electrocochleography (ECochG) to make wave I visible, because they think that it is the best way to verify the diagnosis of cochlear lesion using BERA.

Adolescent↗

Evoked response audiometry and tomography - complementary procedures for the assessment of the deaf infant.

Evoked response audiometry and tomography of the ear both provide highly objective means of assessing certain types of deafness, but both require a general anaesthetic when used to investigate very young children. The use of evoked response audiometry (in particular electrocochleography and brain stem evoked response audiometry) and tomography as combined procedures using the same general anaesthetic is discussed in relation to 15 patients. Their ages ranged from 1 year 3 months to 16 years. All 15 had electrophysiological abnormalities in one or both ears. Abnormalities of the middle and/or inner ear were demonstrated by tomography in 12 patients and in 3 the tomography was normal. In 10 cases both procedures suggested severe or almost total deafness in one or both ears. The demonstration of an anatomical abnormality can be very important in future management with particular reference to surgical reconstructions and the potential development of cerebrospinal fluid fistula.

Adolescent↗

[A practical application of brainstem evoked response audiometry (author's transl)].

After a brief review of Brainstem Evoked Response Audiometry (BERA) for clinical diagnosis of middle and inner ear hearing losses (Fig. 2, 3) and retrocochlear damages a new practical application is presented: Brainstem Evoked Response Audiometry in Tympanoplasty. Recordings of acoustically evoked brainstem potentials have been made in middle ear surgery in order to get direct objective information about the mobility of the stapes (Fig. 4) and the sound conducting mechanism of the middle ear after tympanoplasty (Fig. 5). Because of the damping factor of the middle ear after tympanoplastic reconstruction quantitative evaluation of sound transmission to the internal ear. Via brainstem potentials evoked by loudspeakers or probe tubes is difficult. Therefore, a special mechanical vibrating system for direct stimulation of the middle ear apparatus at various locations will have to be developed.

Audiometry↗

[Evoked response audiometry in circulatory disorders in the brainstem (author's transl)].

In the case of retrocochlear lesions evoked potentials from different stages of the auditory pathway were recorded. Four Patients with nearly normal hearing threshold and normal cortical potentials show reduced medium latency potentials show reduced medium latency potentials due to circulatory dysfunction in the brainstem. Desynchronisation effects on the brainstem level are completely compensated in the cortex. The damage of the auditory pathway could not be found by X-ray or other usual clinical methods. In the two cases described improvement under medical treatment can be demonstrated.

Audiometry↗

Brainstem-evoked response audiometry: normative data from the preterm infant.

Brainstem-evoked response audiometry (BERA) was performed on 40 preterm infants who had low neonatal risk scores. Mean latencies for waves I and V were obtained from four age-groups, 33-34, 35-36, 37-38 and 39-40 weeks conceptional age. The results indicate that BERA is a valuable and reliable tool in assessment of auditory function in the preterm infant. Also for classification of abnormality it is recommended that 2 standard deviations from the mean latency of wave V be used.

Audiometry↗